1. Field of the Invention
The present invention generally relates to a source driver circuit, and more particularly to a source driver circuit of an LCD apparatus.
2. Description of Prior Art
Please refer to FIG. 6, which shows a diagram of a driving circuit of an LCD apparatus according to prior art first. As shown in FIG. 6, the LCD apparatus of prior art mainly comprises a TFT liquid crystal panel 1, a display controller 2 and a gate driver circuit 3 for controlling gate electrodes of the TFT liquid crystal panel 1. The display controller 2 generates a gate driving control signal 4 to control the gate driver circuit 3 and transmits thereto. Furthermore, the LCD apparatus of prior art further comprises a source driver circuit. The source driver circuit includes reference voltage circuits 5 and 6, voltage selectors 7 and 8, DACs 9 and 10 (Digital to Analog Converter), non-invert amplifiers 11 and 12, a shift register 14, a level shifter 15, and a demultiplexer 16. The reference voltage circuits 5 and 6 transform digital display data into gradation voltage signals according to the reference voltages. The DACs 9 and 10 convert voltage data from the voltage selectors 7 and 8 into analog signals respectively. The non-invert amplifier 11 works as an analogue buffer for applying the analogue signals from DAC 9 to the TFT liquid crystal panel 1. The non-invert amplifier 12 also works as an analogue buffer for applying the analogue signals from DAC 10 to the TFT liquid crystal panel 1. The level shifter 15 raises the outputted voltage level of the shift register 14.
The non-invert amplifiers 11 and 12 output display signals 13 that drive the TFT liquid crystal panel 1 to the demultiplexer 16. Furthermore, the display controller 2 transmits a timing signal 17 to the shift register 14 for transmitting the display signals 13 from the demultiplexer 16 to the TFT liquid crystal panel 1. In the meantime, the display controller 2 also transmits a transfer clock 18 to the shift register 14. Moreover, the display controller 2 transmits pulses 19 to the level shifter 15 according to the transfer clock 18.
The display controller 2 outputs the gate driving control signals 4 to the gate driver circuit 3. And then, the controlled gate driver circuit 3 activates any one gate control line of the TFT liquid crystal panel 1.
Display data are the gradation voltage signals which are generated by the reference voltage circuits 5 and 6 for applying to the TFT liquid crystal panel 1. Then, the gradation voltage signals are converted by the DACs 9 and 10. The analog signals obtained by aforesaid conversion are inputted into the non-invert amplifiers 11 and 12. For cyclically reversing the polarities of the gradation voltages applied to the TFT liquid crystal panel 1, the reference voltage circuits 5 and 6, the voltage selectors 7 and 8, the DACs 9 and 10, the non-invert amplifiers 11 and 12 are all the essential elements during driving the liquid crystals.
More specifically, the LCD apparatus of prior arts needs a positive reference voltage circuit 5 and a negative reference voltage circuit 6 for cyclically reversing the polarities of the gradation voltages of driving the liquid crystals of the TFT panel 1. Correspondingly, two voltage selectors 7 and 8, two DACs 9 and 10, two non-invert amplifiers 11 and 12 become necessary. Therefore, an occupied area of the source driver circuit is large and power consumption thereof is also high. For a tendency towards microminiaturization and low power consumption of LCD apparatus s, there is a need to resolve the aforesaid drawbacks to satisfy demands for microminiaturization and low power consumption of LCD apparatus.